Light-sensitive photographic paper and composition



United States Patent O LIGHT-SENSITIVE PHOTOGRAPHIC PAPER AND COMPOSITION William J. Knox, Jr., and Gordon D. Davis, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application May 25, 1953, Serial No. 357,364

5 Claims. (Cl. 95-7) This invention relates to an improved coating process and new product produced thereby. More particularly this invention concerns an improved process for coating. photographic materials onto a base such as a paper base to produce an improved photographic prodnot.

There are many instances in industry where it is desired to apply one or more relatively thin coatings or layers to various type bases. The photographic industry is a particular illustration of where relatively thin coatings are applied to various type bases including paper bases. In obtaining such coatings it is of course highly desirable in many instances that the coatings be relatively uniform and that the base thus coated be free of bare spots or other imperfections. It is also apparent that it is desirable to accomplish such coatings at good production speeds for efiici'ency of operation.

In order to facilitate such coating procedures, it has already been suggested in the art to utilize in the coatings various surface-active agents for facilitating such coating procedures or operations. One such agent which has been described and used is a material known as saponin. While this agent is quite useful and has merit in a: number of respects, as is known it is a natural occurring material of vegetable origin. Therefore, the material may vary from batch to batch, both in quality and in composition. Hence, it is difficult to secure uniformity of results. Also, in some instances photographic work certain batches of this agent may cause an increase in fog in the photographic materials, or a decrease of sensitivity or otherwise present various difiiculties.

Accordingly, there has been considerable work carried out for finding suitable synthetic surface-active agents which may be used for purposes of the above type. Such synthetic agents, because of' the controllable nature of their manufacture, usually would be reproducible from batch to batch both in chemical composition and behavior. While a number of synthetic agents have been discovered which exhibit merit and have considerable utility, it has been noted that they may be deficient in. certain respects. For example, while certain agents materially contribute to the ease of coating, because of their properties of damaging photographic components they may not be used in photographic work. Or other of the coating agents, while improving; in some respects, introduce other problems such as. that additional coatings may not be applied over the first coating containing the agent while it is wet immediately after chilling. to produce gelation. Various other difficulties and problems which have been encountered in this coating field will be referred to as the description proceeds.

It is therefore apparent that providing agents of the class indicated which may be incorporated in coatings, such as photographic coatings, and which facilitate coating operations without the introduction of insurmountable secondary eifects, is a highly desirable result. After extended investigation we have found that a certain group of agents, which will be described in detail hereinafter, may be effectively used in coating operations.

For a still further appreciation of some of the problems involved in the field under consideration, brief reference will now be made to certain apparatus and techniques. One method of coating involves a simple dip coating technique in which both the uniformity and magnitude of the coating thickness are controlled by various devices installed just above the coating pan. With some of the devices used, it isnecessary for the flow of material back into the coating pan to be without turbulence, so that no bubble formation will occur to impair the uniformity of the coating.

This invention has for one object to provide an improved coating method. An important object is to provide a procedure particularly adapted for the coating of various proteinaceous coatings on cellulosic bases.

Another important object is to provide a method for coating photographic coatings such as emulsions upon base materials such as paper. Still another object is to provide an improved coating procedure whereby a first coating may be followed immediately by further coatings with good results. Still another object is to provide a coating procedure of the type aforementioned whereby there is a smooth runback in relation to the leveling device. A still further object is to provide a process which gives the overall result of relatively smooth and uniform coating on the base such as a paper base or other cellulosic type base. Another object is to provide a new product comprising said base carrying a relatively uniform and regular coating, which while containing the surface-active agent of the present invention, possesses unimpaired photographic properties. Other objects will appear hereinafter.

After extensive investigation and study, we have found that a chemical composition which we refer to as a salt of a sulfated and alkylated polyethylene glycol ether, when used in coating procedures, as will be described in further detail hereinafter, gives highly desirable results. The general type of compound we prefer may be illustrated by the following chemical structure:

wherein n may be an integer from 8 to 18, x an integer from 4 to 10 and Me may be a radical such as Na, K, NH4, or mono, di, or triethanolammonium.

The generic formula just set forth may be more specifically illustrated by our preferred reagent having the formula:

C12H25 OCH2CH2) sOSOsNa This is a chemical known as lauryl polyethylene glycol sulfate (sodium salt). These agents may be prepared in a number of ways such as for example by the reaction of a relatively long chain aliphatic alcohol exemplified by lauryl alcohol with ethylene oxide, at low temperatures 40-60 C., followed by sulfation and salt formation. Since the production of the agent per se is not a part of the present invention, further details with respect thereto appear unnecessary.

In general it is preferred that our compound be of an aliphatic nature. This is, the CnHzn 1 radical mentioned above is preferably of the lauryl, oleyl, myristyl, or cetyl type. The (OCHzCHz) grouping usually would be under 10. (The sulfate radical is usually as shown although potassium or other ions beside sodium may be used.) Certain substituents such as hydroxy or carboXy groups, additional double bonds, and the like may be present in the hydrophobic group. It is desired again to mention, however, that the overall structure is preferably aliphatic. This distinction is mentioned to distinguish from a number of agents available on the market which are of an aromatic nature.

Also, reference may be made to the compounds described in our co-workers Patent No. 2,190,645. However, it is desired to point out that such ether compounds are of the non-ionic type whereas our compounds are of the anionic type and thereby distinguish in this and other respects.

The coating materials containing our agent may be of various compositions as will be apparent from the several specific examples which follow. However, for general explanation, reference will be made to proteinaceous coating compositions of a photographic nature. Such coatings are illustrated by gelatin containing various sensitive components such as silver salts. This type of composition is referred to in some detail inasmuch as it concerns our preferred embodiment and also presents more problems than certain other coating compositions. That is, while in the art many kinds of surface-active agents have been added to coating compositions and do facilitate their coating; nevertheless such agents would not be suitable in compositions such as the photographic coatings under description, because such agents might injure the sensitive photographic materials. Hence it is thought that by showing that the present invention functions in an environment of sensitive photographic coatings, it is apparent that where the problem of sensitivity is not present our invention would likewise have utility and application.

As just mentioned, photographic coatings are comprised of a medium such as gelatin which contains the light sensitive material comprising a silver salt such as silver chloride or bromide. The emulsion may likewise contain dyes and various other materials. Inasmuch as a description of emulsion coatings is found in the publication Fundamentals of Photographic Theory by T. H. James and George C. Higgins, published in 1948 by John Wiley & Sons, Inc., chapter 2, further detailed description herein appears unnecessary.

The base to be coated may be composed of any of the usual conventional base materials. In this invention particular reference is made to a paper base. A description of photographic paper is found in Kodak Data Book, 5th edition, Kodak Papers, pages material of this type would preferably be used in the present invention.

The overall coating procedures which may be utilized may comprise any of the standard procedures employed in the industry. For the preferred embodiment of the present invention, procedure of the type briefly referred to above is employed. That is, the preferred paper base is passed around several feed rolls and the coating material is applied by means of a simple dip coating technique. The material so applied is somewhat thicker than is desired on the finished product. In order to reduce the thickness and level the coating, suitable means are utilized to accomplish these results. In the operations in accordance with the present invention, the means may comprise an air jet which is directed angularly against the coating so as to impinge thereon and smooth, spread, and otherwise improve the coating. Other mechanisms may be employed, such as closely adjusted knives, doctor blades or the like.

In any event, it is important that the coating be relatively uniform and that the run-back from the leveling device be comparatively smooth. Irregular run-back results in channeling and contributes to coating unevenness, and also by fostering bubble formation, to the development of bare spots or inadequately coated areas in the 3 and 4. A base i layer. Our invention is particularly advantageous in preventing or reducing these imperfections.

We have found that by incorporating the aliphatic type of anionic agent already described above in detail, into various coating compositions that the coating thereof on various bases is facilitated. A high quality uniform coating may be obtained. The exact thickness of this coating is not a limitation of the present invention as our invention facilitates coating of very thin, the order of from 0.0001 inch thickness say up to 0.001 inch in thickness. Also, we have found that our agent functions satisfactorily at feasible coating speeds.

In practising our invention, the coating composition which it is desired to apply to a base exemplified by the application of a gelatin-silver halide emulsion to a paper base, is prepared in the usual manner. However, at some time before the actual coating operation there is incorporated into the emulsion coating the aliphatic surfaceactive agent of the present invention. This incorporation may be accomplished in the following manner: A 2% solution of the spreading agent is made up. An amount equal to 0.04 to 1.0 gram dry material per pound of coating solution is added to the gelatin-silver halide emulsion at any point after the emulsion is in a liquid state, either before, during, or after the addition of other materials.

While we prefer to incorporate our agent at a later stage in the coating composition preparation, this is not a limitation. Inasmuch as already mentioned our surfaceactive agent is chemically noninjurious photographically it may be incorporated into the composition at earlier stages if this is desired. After the composition is prepared it is placed in suitable coating equipment and the base to be coated passed through the coating device, applying a coating of slightly greater than the desired thickness and concentration as already described. As also mentioned above, this coating is passed in contact with a mechanism, such as devices known as air leveling means, which causes the coating to be spread and otherwise brought to the desired dimensions.

We have found from a study of a number of different coating compositions and operations at various speeds, that our procedure as generically described above substantially facilitates operations and gives an improved coated product.

In addition, one important characteristic of coatings prepared in accordance with the present invention is that they are receptive to the application of another coating thereover immediately after they have been chilled or set. Heretofore in prior operations, wherever certain agents were incorporated, while they facilitated the initial coating, they in some manner produced a finished coating which would not conveniently receive or hold further coatings under these conditions. In contrast thereto, as just mentioned, the coatings of the present invention, even while in an uncured condition, are very receptive to the application of further coatings either of a similar or dissimilar type. In other words, in accordance with the present invention a photographic paper base may be coated with a sensitive gelatinous silver-containing emulsion and this primary coating substantially immediately be given an over-coating with clear gelatin, resins or the like further coatings.

A further understanding of our invention will be had from a consideration of the several specific examples which follow. In these specific examples we have tabulated information from a number of runs wherein our preferred agent, the sodium salt of lauryl polyethylene glycol sulfate, which contained on the average about five ethylene oxide groups between the lauryl group and the sulfate group, was used. It will be observed that this agent was incorporated in a number of different emulsion compositions, the general nature of which is set forth in the table. Also, it will be observed that varying amounts of the agent were incorporated in these runs for determining the general limits of the arnotintof agent which appears most useful.

using relatively small amounts of only a'f racti on of 1% is advantageous not only from the cost standpoint, but is EXAMPLE I.LB. EMULSION MADE-UP OF APPROXIMATELY 8.5 PARTS BY WEIGHT OF GELATIN AND 3.0 PARTS OF SILVER SALT Rfipellengy (1m Concentration Ref. No. of Coating Photographic Sample Run No. gefisligga Runback Quality Sharp Light HIP-483E.-. 28576H..-. a 1 Good-- Satisfactory. PIP-483E--. 28576I..-.. 0 0 2 Excellent... Do.

PIP-48311-.- 28576AA.-. 0.4 0 1 Passable.-;-

Oontrol-...- 28576G...- Std. Level---- 3 1 Excellent...- D0.

EXAMPLE II.-O EMULSION MADE UP OF APPROXIMATELY 7.5 PARTS BY WEIGHT OF GELATIN AND 2.0 PARTS or SILVER SALT! HP-483H-.. 30541A.-.. 0.04 HP-483H... 305MB Oontro1..--. 305410 LIP-483E... 30541D. .40

HP-4S3H-.. 30541E-... 0.80

cocoa.

0 Good 0 Excellent... 0 .....do

0 ..do 0 Passable-...

Satisfactory EXAMPLE IIL-IN EMULSION MADE UP OF APPROXIMATELY 7.4 PARTS BY WEIGHT OF GELATIN AND 1.9 PARTS OF SILVER SALT 1 ELF-483E-.. 305%.... 0.04 111 -48311-.. 30544B--.. 0.2 Gontrol...-. 305440.-.. Std. Level---.

3 Good Satisfactory. Do.

EXAMPLE IV.V EMULSION MADE UP APPROXIMATELY 6.5 PARTS BY WEIGHT OF GELATIN. AND 2.2 PARTS OF SILVER SALT TIP-483E-.. Oontro1.....

Passable.

Satistactory. Do.

EXAMPLE V.IN EMULSION MADE UP OF APPROIXMATELY 5.4 PARTS BY WEIGHT OF GELATIN AND 4.0 PARTS OF SILVER SALT 1 1 In 100 parts of emulsion.

In the above examples by Repellency we refer to number of uncoated spots. By the term standard leve we means 0.78 gram saponin.

In the above examples, in the instance of the V emulsion for example, the coated base resulting from this example was subjected to a further treatment comprising an overcoating with gelatin. The coating obtained was free from defects. This indicated that proceeding in accordance with the present invention, it is possible to overcoat the emulsion coating with further coatings. In this additional work, on overcoating the overcoating compositions which were used in some instances contained saponin, the prior art agent which was described earlier. Therefore it will be observed that the coatings of the present invention were receptive to overcoatings containing other agents or may contain the agents of the present invention.

While it was observed from the several runs referred to above that about 2/ 10 grams of the agent of the present invention added to one pound of the coating composition, namely an amount of agent around 0.05% by weight of the coating composition was quite satisfactory, the invention is not limited to this exact amount. Smaller amounts of the agents of the present invention have utility as do larger amounts, say up to about 0.2% based on the weight of the coating composition. It is preferred not to include too large amounts since the dilution or other physical effect of quantity may ultimately effect certain photographic properties. Accordingly, in general we prefer to use a small amount up to about 0.1% by weight of the coating composition. The capability of an improvement over saponin and other prior art agents which have required the use of appreciably larger quantities.

The percentage concentrations given herein are based on the weight of the wet emulsion rather than of the dried coating.

While in the above examples we have described coating of a conventional photographic paper base, and our invention has particular merit with respect to the coating of such base, it may be utilized in coating procedures where cellulose ester bases, resin bases, or other types of bases are to be coated with thin layers in the manner analogous to the procedure which has been set forth.

Certain other extensions and changes may be made along the following lines. That is, while we have described the coating of flexible film base, this invention may be used in connection with the preparation of coated glass plates for example. While we have described our agent as used alone in coating operations, it may be used in admixture with certain other agents. For example, the agent of the present invention, while the essential component, may have in combination therewith certain other agents such as polyglycerol derivatives, sorbitol monoesters and the like.

We claim:

1. As a new article of manufacture, a light sensitive photographic paper, the article being comprised of a photographic paper base and a light sensitive coating thereon, said coating containing substantial amounts of gelatin and silver salts, and also containing as an essen- 7 tial component 0.01 to 0.02% by weight of the coating of a chemical having the following formula:

2. As a new article of manufacture, photographic paper, the article being comprised of a photographic paper base and a light sensitive coating thereon, said coating containing substantial amounts of gelatin and silver salts, and also containing as an essential component 0.01 to 0.02% by weight of the coating of a chemical having the following formula:

Alkyl OCHzCHz )mOSO3Me wherein x is a number between 4 and10, the alkyl is a radical from the group consisting of lauryl, oleyl, myristyl and cetyl, and Me represents a base substituent from the group consisting of Na, K, and NH-i, mono, di, and triethanol ammonium.

4. A light sensitive suitable for application a light sensitive the alkyl group consisting of lauryl, oleyl,

coating composition particularly to paper, which coating composiv v group consisting of Na,

tion will coatpaper with good run-back and with a minimum of bare spots, said coating composition containing substantial amounts of gelatin and light sensitive silver salts, and also containing as an essential component 0.01 to 0.02% by weight of the coating of a chemical having the following formula:

5. A light sensitive coating composition particularly suitable for application to paper, which coating composition will coat paper with good run-back and with a minimum of bare spots, said coating composition containing substantial amounts of gelatin and light sensitive silver salts, and also containing as an essential component 0.01 to 0.02% by weight of the coating of a chemical having the following formula:

Alkyl OCHzCI-Ia OSO3Me wherein x is a number between 4 and 10, the alkyl is a radical from the group consisting of lauryl, oleyl, myristyl and cetyl, and Me represents a base substituent from the K, and NH4, mono, di, and triet'hanol ammonium.

References Cited in the file of this patent UNITED STATES PATENTS 2,190,645 Boomer Feb. 20, 1940 2,203,768 Baldsiefen June 11, 1940 2,333,809 Nadeau et a1. Nov. 9, 1943 2,415,644 Leonhard et al Feb. 11, 1947 2,572,988 Collins et a1 Oct. 30, 1951 

1. AS A NEW ARTICLE OF MANUFACTURE, A LIGHT SENSITIVE PHOTOGRAPHIC PAPER, THE ARTICLE BEING COMPRISED OF A PHOTOGRAPHIC PAPER BASE AND A LIGHT SENSITIVE COATING THEREON, SAID COATING CONTAINING SUBSTANTIAL AMOUNTS OF GELATIN AND SILVER SALTS, AND ALSO CONTAINING AS AN ESSENTIAL COMPONENT 0.01 TO 0.02% BY WEIGHT OF THE COATING OF A CHEMICAL HAVING THE FOLLOWING FORMULA: 